Oral bacteria live in an environment rich in calcium, due in part to their participation in decalcification of enamel an in part to salivary calcium. Yet little is known of their response to environmental calcium: whether they actively accumulate calcium whether it is involved in cellular metabolism, or whether, like most bacteria, they actively extrude that ion. Streptococci appear to be unique among bacteria in possessing primary calcium and sodium pumps. The goal of this project is to define the calcium metabolism of Streptococcus mutans. The specific aims include 1) development of methodology for measurement of calcium fluxes, 2) energetics of calcium circulation in intact cells, 3) energy coupling of calcium transport by everted vesicles and comparison with the characterized system of S. facaelis, and 4) identification and isolation of calcium transport proteins. The long term objectives include 1) biochemical characterization of such transport proteins and 2) elucidation of the role of calcium transport systems in cellular metabolism and cariogenesis.